1. Field of the Invention
The present invention relates to a voltage control system and to a vehicle comprising the voltage control system.
2. Description of the Related Art
Recently, an electric automobile has been proposed which employs a fuel cell system or the like as a source of drive power for the vehicle. In an electric automobile, driving of the vehicle is implemented by electric motors being driven by electrical power supplied from the power supply, and by the drive wheels of the vehicle being rotated by the rotational force of these electric motors. Since the running stability of this electric automobile is deteriorated if free spinning (slippage) of a vehicle drive wheel occurs while it is running, accordingly recently, as for example disclosed in Japanese Patent Publication No. JP-A-2001-204107, there has been proposed a technique for enhancing the running stability of the vehicle by suppressing the drive force to a vehicle drive wheel if it has been detected that the drive wheel is spinning freely.
By the way, in such an electric automobile, it is usual to provide an accumulator device which supplies auxiliary electrical power, and which can accumulate or discharge electrical energy, in order on the one hand to store regenerated electrical power or surplus electrical power which is generated due to deceleration of the vehicle, and on the other hand to supplement any shortage of the electrical power supplied from the power supply. Moreover, sometimes a voltage control system is employed which is built so as, if a shortage of the electrical power supplied from the power supply occurs, by supplementing this power with electrical power discharged from the accumulator device, to maintain the system voltage at an approximately constant (for example at a predetermined value V0, as shown in FIG. 3D).
With a system which maintains the system voltage at an approximately constant value in this manner, when, due to one of the drive wheels starting to spin freely, the amount of electrical power which is required (i.e. the electrical power consumption of the associated electric drive motor) increases abruptly, as shown in FIG. 3D, the system voltage temporarily decreases abruptly. Due to this, it is arranged to suppress abrupt reduction of the system voltage by supplying electrical power to the system by performing discharge from the accumulator device (as shown by the region indicated by diagonal lines in FIG. 3D).
However when, in the state in which it is arranged to suppress abrupt reduction of the system voltage by performing supply of electrical power from the accumulator device, the drive wheel which is in the freely spinning state touches the ground again and thus rapidly transits into the non-spinning state, since the rotational speed of this drive wheel decreases abruptly and accordingly the required amount of electrical power abruptly decreases, accordingly a state of affairs comes to pass in which the system voltage abruptly increases, as shown in FIG. 3D. When the system voltage abruptly changes in this manner, sometimes it happens that various types of problem can occur, such as deterioration of devices internal to the system, and the like.